There's a debate in my playgroup over a technicality regarding R. Mika::'s ability that reads "...before you take damage from an attack, you may attempt to play a Reversal from your hand...".

The question is what happens with 0 damage attacks. Does her ability still allow playing a reversal to an attack that will deal no damage?

Yes. For all intensive purposes you can still take "0" damage. It just becomes taking no damage so that the attack cannot be added to momentum.

Actually no. An attack at 0 or less damage never counts for dealing damage. Also, I suspect you meant "Intents and purposes" rather then "Intesive purposes."

8.3.3.10 An attack must cause a vitality loss of at least 1 or more to your opponent to be considered to have dealt damage.

Unless they changed the tournament rules since I last read them (and I can't even find them, so who knows), I'd say you're off-base this time Aslum.

8.3.3.10 is relevant to effects triggered or depenant on having dealt damage, as in the past-tense. Otherwise damage reduction effects triggering off being dealt damage could never trigger, as the trigger condition could not be met prior to you actually losing vitality.

At the appropriate step the attack deals an amount of damage equal to the damage of the attack, which can be 0. You may react to an attack dealing 0 damage, you cannot react to an attack having dealt 0 damage, because then 8.3.3.10 has kicked in and disallowed it. This is one of the things I would see changed in the rules to make things simpler and more intuative, but for now, that is how the system works, anyone remember huge rants based on Holding Ground? Same rule applied then.

All you'd actually need to do is change the dealing damage step to make an attack deal damage IF it's a positive number. Then you can dump 8.3.3.10 completely and everything makes logical sense. DO YOU HEAR ME HATA???

Yeah, all attacks have a theoretical point where they'd be "dealing damage" (the damage step) even if that damage is 0 or less - 0 or less damage just won't trigger "if this attack deals damage" or "after an attack deals damage" effects, because the attack didn't end up dealing damage when the time came.

Because R.Mika4's ability resolves before the actual damage step occurs, she basically works on potential just like stuff like Killer Android and the like.

While I can't disagree, this is madness/Sparta! Basically she can turn any reversal into Annu Mutsube.

This was a bit confusing considering how I questioned Fei-Long 4 when it was released. In the end it makes sense.

...until your opponent starts playing around her ability by somehow restricting the number of cards in their hand.

...which is why you'd pack Rootless and Son of a Tycoon.